In order to treat bulk material using a gas, it is known to convey a bed of bulk material continuously over a grate. During this, the gas passes through the grate and then flows through the bed of bulk material. This type of treatment of bulk material using gas is frequently found for example when cooling cement clinker using air.
For conveying the bulk material over the grate, so-called reciprocating grates are known, which comprise overlapping rows of grate plates that are alternately unmoving in the conveying direction and moved back and forth in the conveying direction. A cooler of this type is described in DE-A-37 34 043.
Also known in the prior art are so-called moving floor coolers, in which the grate comprises a plurality of bars that are elongate in the conveying direction and are moved forward in the conveying direction at the same time and then back again at different times. During this, the bars move on rollers that are arranged on a steel substructure. It is also possible to provide on the steel substructure—and hence below the grate—air baffles or air chambers, by means of which flow through the grate and through the bulk material lying thereon can be made to differ over the width and/or length of the cooler. Examples of coolers of this type can be found inter alia in DK-A-1999/1403, U.S. Pat. No. 2,240,590 or DE-A-196 51 741.
In both the above-mentioned types of cooler construction, there is always provided a housing by means of which the space above the grate is separated from the surrounding area. As a result, the gas flowing through the bed of bulk material may be collected and supplied to a further use. In the case of a cooler for hot cement clinker, the correspondingly collected, heated cooling air may be used for example for the upstream kiln, for pre-heating the raw material and/or for power generation.
The upper parts of bulk material coolers, which delimit the space above the grate, typically comprise a steel casing, against the inner side of which masonry or another fire-resistant layer is constructed. A corresponding protective layer is required to protect the steel casing from wear.
In the case of a complete new construction of a cooler, the upper part may be erected such that the dimensions correspond to the grate and the substructure below it. Since a corresponding complete new construction of a cooler is costly, the possibility is frequently considered of obtaining parts—in particular the upper part—of an old, already existing bulk material cooler and of equipping it with a new grate and where appropriate a new grate substructure. Because of the improved wear properties, in this case reciprocating grate coolers are frequently to be converted into moving floor coolers.
Because of the prerequisites of manufacturing technology, and in order to avoid costly customized manufacture, however, the bars of a moving floor cooler typically have standardized (at least the manufacturer's own) dimensions, in particular a standardized width. The steel substructure is also adjusted to this standardized bar width, as a result of which a low-cost modular substructure system is made possible.
If an existing bulk material cooler upper part is to be equipped with a new moving floor cooler, the problem frequently occurs that the internal width of the upper part does not correspond to a whole number of multiples of the standard width of bars. To solve this problem, according to the prior art a moving floor cooler having a bar width that is adjusted to the existing upper part can be manufactured, although this means a costly customized manufacture. As an alternative, it is known to reduce the internal width of the upper part by constructing additional masonry or another fire-resistant layer such that this dimension corresponds to a multiple of a standard width for bars. However, a solution of this type is complex and moreover results in a grate surface area of the new moving floor cooler that is smaller than the original reciprocating grate cooler.